Defect Equilibration in Amorphous Silicon Films Submitted to High Intensity Illumination

1996 ◽  
Vol 420 ◽  
Author(s):  
C. Godet ◽  
P. Roca i Cabarrocas
Keyword(s):  
High Intensity ◽  
Urbach Energy ◽  
Defect Density ◽  
Fast Kinetics ◽  
Slow Kinetics ◽  
Wide Range ◽  
Medium Range ◽  
Infrared Signature ◽  
Kinetics Of ◽  
Creation Rate

AbstractIn plasma-deposited a-Si:H films, the increase of the metastable defect density produced by high-intensity illumination usually follows a stretched-exponential time-dependence, with a characteristic time τSE and a steady-state value Nss. For a wide range of deposition conditions, we have observed that both parameters depend on the material properties. The strong correlation between Nss and the monohydride [SiH]2000 density, reported previously, has been interpreted as due to the trapping of metastable H atoms at specific sites.In this study of the kinetics of defect equilibration under high-intensity illumination, we find two groups of a-Si:H films with fast and slow kinetics, respectively. These two groups display a very different dependence of the defect creation rate as a function of the optical gap. For the fast kinetics films, we emphasize the critical influence of the Urbach energy Eu deduced from the exponential optical absorption edge (1/τSE increases as a function of Eu). The slow kinetics films are characterized by a high nanovoid density evidenced by their SiHx infrared signature at 2090 cm-1. The results are discussed in relation to the medium-range H motion.

Metastability Under High-Intensity Light of Device-Quality He-Diluted, H2-Diluted and Standard a-Si:H Films Deposited Between 50°C and 350°C

1994 ◽  
Vol 336 ◽  
Author(s):  
P. Morin ◽  
P. Roca i Cabarrocas
Keyword(s):  
High Intensity ◽  
Defect Density ◽  
Red Light ◽  
Rf Power ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Kinetics Of ◽  
Defect Densities ◽  
High Intensity Light

ABSTRACTWe report the results of a study of the metastability under illumination by high intensity red light of device quality a-Si:H thin films deposited using a wide range of deposition conditions. The process variables included substrate temperature, pressure, rf power, and dilution of silane by He or H2. In-situ Monitoring of the sample conductivity and defect density during light-soaking provides the kinetics of the degradation of the electronic properties of the films. We observe equilibration of the photoconductivity and of the defect density. The characteristic time of equilibration τse of the defect density varies by more than an order of magnitude, dividing the samples into two groups: one group with a τse on the order of 103 seconds, the other with a τse on the order of 104 seconds. Low steady state defect densities combined with high ημτ products are observed for “standard” a-Si:H deposited between 100°C and 250°C and He-diluted films deposited above 250°C.

An Alternative Model for the Kinetics of Light-Induced Defects in A-Si:H

1991 ◽  
Vol 219 ◽  
Author(s):  
Paulo V. Santos ◽  
W. B. Jackson ◽  
R. A. Street
Keyword(s):  
Time Dependence ◽  
Valence Band ◽  
Defect Formation ◽  
Defect Density ◽  
Generation Rate ◽  
Band Tail ◽  
Defect Generation ◽  
Wide Range ◽  
Induced Defects ◽  
Kinetics Of

ABSTRACTThe kinetics of light-induced defect generation in a-Si:H was investigated over a wide range of illumination intensities and temperatures. The defect density around 1016cm-3 exhibits a power-law time dependence Ns ∼ G2εfε with ε = 0.2 to 0.3, where G is the photo-carrier generation rate. A model for the kinetics of defect generation is proposed based on the existence of an exponential distribution of defect formation energies in the amorphous network, associated with the valence band tail states. The model reproduces the observed time dependence of the defect density with an exponent e determined by the exponential width of the valence band tail. The temperature dependence of the defect generation rate is well-reproduced by the model, which provides a connection between the Stabler-Wronski effect and the weak-bond model.

Recovery Kinetics of Phosphorus Ion-Implanted a-Si:H

1996 ◽  
Vol 420 ◽  
Author(s):  
J. Nakata ◽  
S. Wagner ◽  
H. Gleskova ◽  
P. A. Stolk ◽  
J. M. Poate
Keyword(s):  
Gas Phase ◽  
Thermal Activation ◽  
Urbach Energy ◽  
Defect Density ◽  
Strained Si ◽  
Effective Electron ◽  
Additional Illumination ◽  
Hydrogenated Amorphous ◽  
Kinetics Of ◽  
Strained Bonds

AbstractHydrogenated amorphous silicon was implanted with phosphorus ions to a uniform concentration of 3×1020 cm-3 and defect saturation. The implants were annealed isochronally up to 400°C in the dark or under additional illumination. This illumination had no effect on recovery. The Urbach energy remains higher than that of silicon-implants. The midgap defect density anneals to ˜ 1018 cm-3, typical of gas-phase doped samples. The dark conductvity remains lower and its thermal activation energy higher than in gas-phase doped samples. We surmise that the Si-Si network absorbs some of the donor electron-induced defect density by forming strained Si-Si bonds. These strained bonds widen the band tails, and thus reduce the effective electron mobility and pin the Fermi level.

scholarly journals The Role of Distal S6 Hydrophobic Residues in the Voltage-dependent Gating of CaV2.3 Channels

2007 ◽  
Vol 282 (38) ◽  
pp. 27944-27952 ◽  
Author(s):  
Alexandra Raybaud ◽  
Ebru-Eylem Baspinar ◽  
François Dionne ◽  
Yolaine Dodier ◽  
Rémy Sauvé ◽  
...  
Keyword(s):  
Relative Stability ◽  
Critical Role ◽  
Three Dimensional ◽  
Inactivation Kinetics ◽  
Significant Shift ◽  
Fast Kinetics ◽  
Hydrophobic Residues ◽  
Closed State ◽  
Slow Kinetics ◽  
Kinetics Of

The hydrophobic locus VAVIM is conserved in the S6 transmembrane segment of domain IV (IVS6) in CaV1 and CaV2 families. Herein we show that glycine substitution of the VAVIM motif in CaV2.3 produced whole cell currents with inactivation kinetics that were either slower (A1719G ≈ V1720G), similar (V1718G), or faster (I1721G ≈ M1722G) than the wild-type channel. The fast kinetics of I1721G were observed with a ≈+10 mV shift in its voltage dependence of activation (E0.5,act). In contrast, the slow kinetics of A1719G and V1720G were accompanied by a significant shift of ≈-20 mV in their E0.5,act indicating that the relative stability of the channel closed state was decreased in these mutants. Glycine scan performed with Val 349 in IS6, Ile701 in IIS6, and Leu1420 in IIIS6 at positions predicted to face Val1720 in IVS6 also produced slow inactivating currents with hyperpolarizing shifts in the activation and inactivation potentials, again pointing out a decrease in the stability of the channel closed state. Mutations to other hydrophobic residues at these positions nearly restored the channel gating. Altogether these data indicate that residues at positions equivalent to 1720 exert a critical control upon the relative stability of the channel closed and open states and more specifically, that hydrophobic residues at these positions promote the channel closed state. We discuss a three-dimensional homology model of CaV2.3 based upon Kv1.2 where hydrophobic residues at positions facing Val1720 in IS6, IIS6, and IIIS6 play a critical role in stabilizing the closed state in CaV2.3.

Scintigraphic studies in rats. Kinetics of insulin analogues covering wide range of receptor affinities

Diabetes ◽  
1991 ◽  
Vol 40 (5) ◽  
pp. 628-632 ◽  
Author(s):  
I. Jensen ◽  
V. Kruse ◽  
U. D. Larsen
Keyword(s):  
Insulin Analogues ◽  
Wide Range ◽  
Kinetics Of

Single atom catalysts supported on N-doped graphene toward fast kinetic Li−S batteries: a theoretical study

2021 ◽  
Author(s):  
Xu Han ◽  
Zeyun Zhang ◽  
Xuefei Xu
Keyword(s):  
Theoretical Study ◽  
Single Atom ◽  
Discharge Process ◽  
Fast Kinetics ◽  
Shuttle Effect ◽  
Sufficient Stability ◽  
Doped Graphene ◽  
Fast Kinetic ◽  
Kinetics Of ◽  
Charge Discharge

To suppress the shuttle effect of lithium polysulfides and promote fast kinetics of charge−discharge process in Li−S batteries, it is essential to search promising catalysts with sufficient stability and high...

scholarly journals Microstructure, Hardness, and Elastic Modulus of a Multibeam-Sputtered Nanocrystalline Co-Cr-Fe-Ni Compositional Complex Alloy Film

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3357
Author(s):  
Péter Nagy ◽  
Nadia Rohbeck ◽  
Zoltán Hegedűs ◽  
Johann Michler ◽  
László Pethö ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Crystallite Size ◽  
Physical Vapor Deposition ◽  
Defect Density ◽  
Lattice Defect ◽  
Chemical Compositions ◽  
Line Profile Analysis ◽  
Face Centered Cubic ◽  
Complex Alloy ◽  
Wide Range

A nanocrystalline Co-Cr-Ni-Fe compositional complex alloy (CCA) film with a thickness of about 1 micron was produced by a multiple-beam-sputtering physical vapor deposition (PVD) technique. The main advantage of this novel method is that it does not require alloy targets, but rather uses commercially pure metal sources. Another benefit of the application of this technique is that it produces compositional gradient samples on a disk surface with a wide range of elemental concentrations, enabling combinatorial analysis of CCA films. In this study, the variation of the phase composition, the microstructure (crystallite size and defect density), and the mechanical performance (hardness and elastic modulus) as a function of the chemical composition was studied in a combinatorial Co-Cr-Ni-Fe thin film sample that was produced on a surface of a disk with a diameter of about 10 cm. The spatial variation of the crystallite size and the density of lattice defects (e.g., dislocations and twin faults) were investigated by X-ray diffraction line profile analysis performed on the patterns taken by synchrotron radiation. The hardness and the elastic modulus were measured by the nanoindentation technique. It was found that a single-phase face-centered cubic (fcc) structure was formed for a wide range of chemical compositions. The microstructure was nanocrystalline with a crystallite size of 10–27 nm and contained a high lattice defect density. The hardness and the elastic modulus values measured for very different compositions were in the ranges of 8.4–11.8 and 182–239 GPa, respectively.

scholarly journals Non-Coding RNAs in the Transcriptional Network That Differentiates Skeletal Muscles of Sedentary from Long-Term Endurance- and Resistance-Trained Elderly

2021 ◽  
Vol 22 (4) ◽  
pp. 1539
Author(s):  
Paola De Sanctis ◽  
Giuseppe Filardo ◽  
Provvidenza Maria Abruzzo ◽  
Annalisa Astolfi ◽  
Alessandra Bolotta ◽  
...  
Keyword(s):  
Exercise Training ◽  
High Intensity ◽  
Vastus Lateralis ◽  
Mammalian Target Of Rapamycin ◽  
Differentially Expressed ◽  
Transcriptional Networks ◽  
Vastus Lateralis Muscle ◽  
Age Related ◽  
Wide Range ◽  
Non Coding Rnas

In a previous study, the whole transcriptome of the vastus lateralis muscle from sedentary elderly and from age-matched athletes with an exceptional record of high-intensity, life-long exercise training was compared—the two groups representing the two extremes on a physical activity scale. Exercise training enabled the skeletal muscle to counteract age-related sarcopenia by inducing a wide range of adaptations, sustained by the expression of protein-coding genes involved in energy handling, proteostasis, cytoskeletal organization, inflammation control, and cellular senescence. Building on the previous study, we examined here the network of non-coding RNAs participating in the orchestration of gene expression and identified differentially expressed micro- and long-non-coding RNAs and some of their possible targets and roles. Unsupervised hierarchical clustering analyses of all non-coding RNAs were able to discriminate between sedentary and trained individuals, regardless of the exercise typology. Validated targets of differentially expressed miRNA were grouped by KEGG analysis, which pointed to functional areas involved in cell cycle, cytoskeletal control, longevity, and many signaling pathways, including AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR), which had been shown to be pivotal in the modulation of the effects of high-intensity, life-long exercise training. The analysis of differentially expressed long-non-coding RNAs identified transcriptional networks, involving lncRNAs, miRNAs and mRNAs, affecting processes in line with the beneficial role of exercise training.

scholarly journals Effects of Two Workload-Matched High-Intensity Interval Training Protocols on Regional Body Composition and Fat Oxidation in Obese Men

Nutrients ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 1096
Author(s):  
Spyridon Tsirigkakis ◽  
George Mastorakos ◽  
Yiannis Koutedakis ◽  
Vassilis Mougios ◽  
Alan M. Nevill ◽  
...  
Keyword(s):  
Body Composition ◽  
High Intensity ◽  
Interval Training ◽  
Fat Oxidation ◽  
Peak Oxygen Uptake ◽  
High Intensity Interval Training ◽  
Randomized Design ◽  
Wide Range ◽  
Regional Body Composition ◽  
High Intensity Interval

The effects of two high-intensity interval training (HIIT) protocols on regional body composition and fat oxidation in men with obesity were compared using a parallel randomized design. Sixteen inactive males (age, 38.9 ± 7.3 years; body fat, 31.8 ± 3.9%; peak oxygen uptake, VO2peak, 30.9 ± 4.1 mL/kg/min; all mean ± SD) were randomly assigned to either HIIT10 (48 × 10 s bouts at 100% of peak power [Wpeak] with 15 s of recovery) or HIIT60 group (8 × 60 s bouts at 100% Wpeak with 90 s of recovery), and subsequently completed eight weeks of training, while maintaining the same diet. Analyses of variance (ANOVA) showed only a main effect of time (p < 0.01) and no group or interaction effects (p > 0.05) in the examined parameters. Total and trunk fat mass decreased by 1.81 kg (90%CI: −2.63 to −0.99 kg; p = 0.002) and 1.45 kg (90%CI: −1.95 to −0.94 kg; p < 0.001), respectively, while leg lean mass increased by 0.86 kg (90%CI: 0.63 to 1.08 kg; p < 0.001), following both HIIT protocols. HIIT increased peak fat oxidation (PFO) (from 0.20 ± 0.05 to 0.33 ± 0.08 g/min, p = 0.001), as well as fat oxidation over a wide range of submaximal exercise intensities, and shifted PFO to higher intensity (from 33.6 ± 4.6 to 37.6 ± 6.7% VO2peak, p = 0.039). HIIT, irrespective of protocol, improved VO2peak by 20.0 ± 7.2% (p < 0.001), while blood lactate at various submaximal intensities decreased by 20.6% (p = 0.001). In conclusion, both HIIT protocols were equally effective in improving regional body composition and fat oxidation during exercise in obese men.

Improvement of the Detection Sensitivity of Edxrf Trace Element Analysis by Means of Efficient X-Ray Focusing Based on Strongly Curved Hopg Crystals

1995 ◽  
Vol 39 ◽  
pp. 109-117
Author(s):  
Burkhard Beckhoff ◽  
Birgit Kanngießer
Keyword(s):  
High Intensity ◽  
Focal Plane ◽  
Bragg Reflection ◽  
Pyrolytic Graphite ◽  
Trace Element Analysis ◽  
Detection Sensitivity ◽  
Element Analysis ◽  
X Ray ◽  
Wide Range ◽  
Very High

X-ray focusing based on Bragg reflection at curved crystals allows collection of a large solid angle of incident radiation, monochromatization of this radiation, and condensation of the beam reflected at the crystal into a small spatial cross-section in a pre-selected focal plane. Thus, for the Bragg reflected radiation, one can achieve higher intensities than for the radiation passing directly to the same small area in the focal plane. In that case one can profit considerably from X-ray focusing in an EDXRF arrangement. The 00 2 reflection at Highly Oriented Pyrolytic Graphite (HOPG) crystals offers a very high intensity of the Bragg reflected beam for a wide range of photon energies. Furthermore, curvature radii smaller than 10 mm can be achieved for HOPG crystals ensuring efficient X-ray focusing in EDXRF applications. For the trace analysis of very small amounts of specimen material deposited on small areas of thin-filter backings, HOPG based X-ray focusing may be used to achieve a very high intensity of monochromatic excitation radiation.

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